Contemporary two-storey churches – acoustic investigations

Abstract

The paper discusses the issue of contemporary two-storey churches in Poznań. The analysis of the issue was carried out on the basis of investigations in five two-storey churches in Poznań. The churches under investigation were: Visitation of Blessed Virgin Mary Church, Christ the King Church, Our Lady of Częstochowa Church, St. Lawrence Church, and Christ the Redeemer Church. In total, ten interiors were examined. The churches were erected in the late 70s and early 80s of the 20th century. The issue of acoustics in churches is complex, as church interiors must promote functions of extreme acoustic requirements. Intelligibility of speech is crucial, being the basis of the Catholic liturgy. However, the organ is inherent in the liturgy, too. For organ music, the recommended acoustic parameters are entirely different from those for speech. Two-storey churches are particularly interesting in terms of acoustics because they are composed of two interiors with different acoustic properties. As a rule, the upper church is usually bigger and more decorative. The acoustic investigations were conducted by means of an omnidirectional sound source, a SVAN 945A Sound Level Meter and the DIRAC programme. The e-sweep signal was generated and RT, Ts , C80 and C50 were measured. The Brüel & Kjær ZE-0948 USB Audio Interface was used. The investigated acoustic parameters were compared with recommendations. The paper discusses the idea of two-storey churches, with insight into socio-political conditions which influenced their construction. The acoustic conditions were analysed in terms of cubature, the shape of the interior and finishes. The upper and lower churches were compared within one building; the investigation also involved comparing the churches against each other. Moreover, functionality of the buildings was analysed, which included aspects of acoustic as well as architectural functionality. In the analysed buildings, contemporary construction solutions were applied. Load bearing elements of the ceiling and roof construction were made either of monolithic reinforced concrete or by means of steel trusses. Such solutions enable covering of considerable spans without application of intermediate supports. This has a large influence on the acoustics of the interior as the lack of subspaces affects excessive reverberation.